I'm helping a friend out with her 2007 Prius. She was having issues with it and took it to the dealership. Told her the battery is bad and needs replaced. Quoted $5000+. I know this is something I can do, but she can't afford even $1000 right now. I took the battery out and started by taking all the bus bars off and cleaning the corrosion. Put a volt meter on the individual cells and most read 8.15v-8.2v. I had 2 that read 7.8v and 1 that read 7.0v. Would this cause drivability issues and cause the P0A80, B1271 and P3000 codes? Can this be repaired by replacing the 1 cell, or the 3? A lot of what I seem to find show the cell voltage should be around 7.2v. Could the others all be reading high? Thanks for any help you can provide. Here's a pic of the codes
Yes, but voltage is only part of the equation. You need to put a "load" across the battery to see how well the perform - stress test them. If your battery can't sustain voltage under load, it won't be able to drive your electric motors. I bet you multiple batteries will fail a load test.
Do you know if the Autel MK900 is capable of performing any tests on the battery system? Is the 8.2v seem high, or is that normal?
^ +1 I will also say that a static voltage measurement of a hybrid battery module will only give you limited information. Looking at the voltages when the module is under load is a better way to determine if it is bad. The HV battery pack is made up of 28 modules. Each module has six 1.2v (nominal) cells inside, which are wired in series. So, the nominal voltage of a module is 7.2 volts (6 cells × 1.2v = 7.2v). When the battery is charged, the voltage of a module will increase up to -8.7v. All the modules are connected in series, so one bad cell within a module will cause a problem. There are a total of 168 cells in the hybrid battery pack (6 cells per module × 28 modules = 168 cells total). Based on your measured voltages of the modules, you have at least one bad module that needs to be replaced. The 7.0v module will cause the P0A80 code and maybe the P3000 code, but not the B1271 code.
B1271 is usually caused by a bad capacitor on the Combination Meter circuit board. The symptom is that the "speedometer" won't turn on when you try to power up the car. Unrelated to the battery problems. You CAN replace the three modules that have lower voltages. It is VERY unlikely that it will work. The battery has 28 modules (6 x 1.2V cells for 7.2V nominal) that are monitored in pairs (so 14 "blocks"). The modules degrade some (lose effective capacity) with time and use. As long as they do so evenly, there's no real cause for concern. The battery ecu monitors all block voltages under different conditions - idling, accelerating, decelerating, etc. The ecu won't set codes if the voltage differential doesn't go above 0.3V for more than a few seconds. Eventually one or more modules can have a cell failure ("big" voltage difference along with code P0A80.) The problem with just replacing a few modules is that it's extremely unlikely that the "new" ones have the same effective capacity and State Of Charge as the existing ones. That leads to high voltage differential at some point and repeat codes. There are MANY posts in the forums about module replacement - use the search feature. Options: Replace modules and cross fingers. Replace modules and use chargers to "refurbish" the pack. Buy a "refurbished" pack (understand the warranty). Buy a (good) used pack from a junkyard. Buy a new pack from Toyota. Posted via the PriusChat mobile app.
I appreciate the help on here. It looks like we're going for the cross the fingers and hope method. She is in such a tight spot that that is her only real option at this time. She's hoping this gets her through to the summer, at which time she'll be in a better financial situation. I'll post my success or failure however it turns out. Again, thank you for the guidance.
